Low Polymerase Activity Attributed to PA Drives the Acquisition of the PB2 E627K Mutation of H7N9 Avian Influenza Virus in Mammals
Low Polymerase Activity Attributed to PA Drives the Acquisition of the PB2 E627K Mutation of H7N9 Avian Influenza Virus in Mammals
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PA 的低聚合酶活性促使哺乳动物获得 H7N9 禽流感病毒的 PB2 E627K 突变
DOI：
10.1128/mbio.01162-19
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发表时间：
2019-05-01
期刊：
影响因子：
6.4
通讯作者：
Li, Chengjun
中科院分区：
文献类型：
--
作者：
Liang, Libin;Jiang, Li;Li, Chengjun
禽流感病毒(AIV)必须获得哺乳动物适应性突变，才能在人类体内有效复制和传播。已知PB2 E627K突变在AIV的哺乳动物适应中起重要作用。2013年在中国出现的H7N9 AIV在人类复制时很容易获得PB2 E627K突变。在这里，我们产生了一系列重新配对或突变的H7N9禽流感病毒，并在小鼠身上进行了测试。我们表明，在H7N9禽流感病毒复制过程中，病毒PA蛋白引起的低聚合酶活性是PB2 E627K出现的内在驱动力。PA N-末端的四个残基在介导PB2 E627K获得过程中起关键作用。值得注意的是，由于病毒PA蛋白的同一性，H7N9 AIV的聚合酶活性和生长对人ANP32A蛋白表达水平的变化高度敏感。此外，ANP32A缺失导致H7N9禽流感病毒的病毒聚合酶活性受损，导致Anp32a(-/-)小鼠的病毒复制减少，取消了获得PB2 E627K突变的机会，而是驱使病毒获得替代的PB2 D701N突变。综上所述，我们的研究结果表明，H7N9禽流感病毒PB2 E627K突变的出现是由病毒PA蛋白固有的低聚合酶活性驱动的，这也涉及哺乳动物ANP32A的参与。2013年出现的H7N9 AIV在获得人类PB2 E627K突变方面具有突出的能力。在这里，我们证明了H7N9 PB2 E627K突变的获得是由病毒PA蛋白在人类细胞中提供的低聚合酶活性驱动的，四个PA残基共同参与了这一过程。值得注意的是，H7N9 PA蛋白导致病毒聚合酶功能对人ANP32A蛋白的显著依赖，而Anp32a基因敲除会取消小鼠中PB2 E627K的获得。这些发现表明，在H7N9禽流感病毒适应人类的过程中，病毒PA和宿主ANP32A对PB2 E627K的出现至关重要。
Avian influenza viruses (AIVs) must acquire mammalian-adaptive mutations before they can efficiently replicate in and transmit among humans. The PB2 E627K mutation is known to play a prominent role in the mammalian adaptation of AIVs. The H7N9 AIVs that emerged in 2013 in China easily acquired the PB2 E627K mutation upon replication in humans. Here, we generate a series of reassortant or mutant H7N9 AIVs and test them in mice. We show that the low polymerase activity attributed to the viral PA protein is the intrinsic driving force behind the emergence of PB2 E627K during H7N9 AIV replication in mice. Four residues in the N-terminal region of PA are critical in mediating the PB2 E627K acquisition. Notably, due to the identity of viral PA protein, the polymerase activity and growth of H7N9 AIV are highly sensitive to changes in expression levels of human ANP32A protein. Furthermore, the impaired viral polymerase activity of H7N9 AIV caused by the depletion of ANP32A led to reduced virus replication in Anp32a(-/-) mice, abolishing the acquisition of the PB2 E627K mutation and instead driving the virus to acquire the alternative PB2 D701N mutation. Taken together, our findings show that the emergence of the PB2 E627K mutation of H7N9 AIV is driven by the intrinsic low polymerase activity conferred by the viral PA protein, which also involves the engagement of mammalian ANP32A.IMPORTANCE The emergence of the PB2 E627K substitution is critical in the mammalian adaptation and pathogenesis of AIV. H7N9 AIVs that emerged in 2013 possess a prominent ability in gaining the PB2 E627K mutation in humans. Here, we demonstrate that the acquisition of the H7N9 PB2 E627K mutation is driven by the low polymerase activity conferred by the viral PA protein in human cells, and four PA residues are collectively involved in this process. Notably, the H7N9 PA protein leads to significant dependence of viral polymerase function on human ANP32A protein, and Anp32a knockout abolishes PB2 E627K acquisition in mice. These findings reveal that viral PA and host ANP32A are crucial for the emergence of PB2 E627K during adaptation of H7N9 AIVs to humans.